1. Field of the Invention
This invention relates to external combustion heat engines.
2. Discussion of the Known Art
Typical external combustion engines include steam engines and so-called Stirling-cycle engines. In contrast to internal combustion engines wherein a liquid or gaseous fuel is repeatedly ignited and burned inside one or more working cylinders, external combustion engines are characterized in that they burn fuel continuously in a chamber that is separate from a cylinder or other space where useful work is produced by the engine.
U.S. Pat. No. 431,729 (Jul. 8, 1890) in the name of John Ericsson discloses an air engine having a working cylinder, a supply cylinder, and an air heater. Work and supply pistons associated with the two cylinders are connected to reciprocate in unison with one another, and the work piston is connected by a rod to a crankshaft having a flywheel. Outside air is admitted into the supply cylinder through a first timed valve mechanism and, upon a compression stroke of the supply piston, is piped into a jacket that surrounds the heater. Hot air from the heater is then admitted into the working cylinder through a second timed valve mechanism to initiate a work stroke of the work piston. See also U.S. Pat. No. 5,894,729 (Apr. 20, 1999) which discloses an afterburning Ericsson cycle engine.
International Application No. PCT/NO97/00022 (WO 97/28362) published Aug. 7, 1997, discloses a two-cycle free-piston diesel gas generator, wherein a pair of free pistons are disposed inside a single cylinder for synchronously opposed reciprocating movement. Heated gas is produced from combusted fuel inside the cylinder, and the gas is expelled by the pistons to be used, for example, to power an external gas turbine. See also, T. A. Johansen, et al., “Free-Piston Diesel Engine Dynamics and Control” (www.itk.ntnu.no/ansatte/Johansen_Tor.Arne/klc_acc. pdf), which also discloses the concept of using a free-piston diesel or “Pescara” engine for producing a supply of hot gas which is used to fuel a turbine power plant.
As far as is known, an engine wherein an externally combusted hot gas product is charged under pressure with a determined timing into a working cylinder of the engine, and a piston in the cylinder is urged by the pressurized gas product to rotate a crankshaft from which power can be taken, has not been disclosed.